错误：
gem install rmagick -v '2.13.1'
Building native extensions. This could take a while...
ERROR: Error installing rmagick:
ERROR: Failed to build gem native extension.
/home/jiahe/.rvm/rubies/ree-1.8.7-2011.03/bin/ruby extconf.rb
checking for Ruby version >= 1.8.5... yes
checking for gcc... yes
checking for Magick-config... no
Can't install RMagick 2.13.1. Can't find Magick-config in /home/jiahe/.rvm/gems/ree-1.8.7-2011.03/bin:/home/jiahe/.rvm/gems/ree-1.8.7-2011.03@global/bin:/home/jiahe/.rvm/rubies/ree-1.8.7-2011.03/bin:/home/jiahe/.rvm/gems/ree-1.8.7-2011.03/bin:/home/jiahe/.rvm/gems/ree-1.8.7-2011.03@global/bin:/home/jiahe/.rvm/rubies/ree-1.8.7-2011.03/bin:/home/jiahe/.rvm/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/home/jiahe/.rvm/rubies/ree-1.8.7-2011.03/bin/ruby解决方案：
sudo apt-get install imagemagick libmagickwand-dev